www/gitea: Update to 1.20.4 (fixes security vulnerabilities)

This release contains one security fix, as well as a number of enhancements
and bug fixes. See the release notes for details.

Release notes:

• https://blog.gitea.com/release-of-1.20.4
• https://github.com/go-gitea/gitea/releases/tag/v1.20.4

PR: 273691
MFH: 2023Q3
Security: 4061a4b2-4fb1-11ee-acc7-0151f07bc899